1. Technical field
The present invention relates to a method for manufacturing a printed circuit board for mounting a semiconductor device and other electronic components.
2. Description of the Related Art
There are known in the art plastic packages in which ICs, LSIs, or other semiconductor chips are mounted on a printed circuit board, and a resin is injected into the chip mounting section to seal the package. A BGA (ball grid array) configuration is commonly used for such plastic packages in order to provide a larger number of terminals for the semiconductor chips to be mounted and to reduce the size of the package.
A plurality of bonding pads, conductive wires, and the like are formed on the obverse surface of printed circuit boards used in BGA-type plastic packages, while a plurality of solder ball pads for forming solder balls as external connection terminals is formed in a grid shape on the reverse surface. Each of the solder ball pads is electrically connected to conductive wiring that includes bonding pads formed on the surface of the board via through-holes formed in the printed circuit board. It is thereby possible for I/O signals to be routed from external connection terminals on the reverse surface of the printed circuit board. The bonding pads and the solder ball pads are ordinarily plated with Au in order to ensure the solder balls and the bonding wires are joined with adequate strength.
FIG. 1 is a plan view schematically showing the configuration of a conventional printed circuit board 100, the configuration being on the reverse side of the board, which is the side opposite from the chip-mounting surface. A plating tie bar 110 (tie bar for plating) is formed on base material 200 so as to surround the periphery of the printed circuit board 100. A plurality of plating lead wires 120 (lead wire for plating) that extend toward through-holes 130 and the solder ball pads 140 from the tie bar 110 are formed. The plating lead wires 120 are independently provided to each of the through-holes 130 and solder ball pads 140. For this reason, the plating lead wires 120 connected to the solder ball pads 140 positioned in the center portion of the plastic board are arranged so as to weave between other solder ball pads and plating lead wires. The Au-plating process used on the solder ball pads 140 is carried out by electroplating, wherein each of the solder ball pads is energized via the plating lead wires 120 and the plating tie bar 110 in the plating bath. The base material 200 is cut along a cut line 300, whereby the printed circuit board 100 is formed into smaller pieces.